Truck box covers are used to protect loads that are susceptible to damage from water, fumes, wind, snow and other environmental elements encountered during storage and transit. Covers are also used to prevent loads including sand, dirt, gravel and wood chips falling out onto the roads and adjacent vehicles. Dump truck covers are desirable to prevent dirt, gravel, sand or refuse from falling onto the road or vehicles which often suffer cracked windshields and chipped paint. A number of states in the United States of America and Europe and Canadian provinces have laws that require truck boxes and trailers to be covered during transit.
The operators of the trucks have the job of opening and closing the covers. Covers with hand cranks require considerable time and effort to operate and are at locations that are not readily accessible Examples of a hand crank drive for a truck cover is disclosed by H. E. Thurston in U.S. Pat. No. 3,977,719. The truck operators must leave the cabs of the trucks to close and open the covers or have assistants to open and close the covers. Power operated truck box covers have been developed to reduce the time and labor required to open and close the covers. D. B. Richard in U.S. Pat. No. 4,050,734 uses hydraulic cylinders to swing an inverted U-shaped bar pivoted to the sides of a truck to carry a cover between open and closed positions When the cover is in the closed position the load is not totally enclosed within the truck so that material can fall out onto the road or hit a vehicle.